Transportation of large quantities of a liquid cryogen, e.g. helium, from the production plant to a distant location is usually accomplished by liquefying the gas, transfering the liquid into an insulated tank, transporting the tank to a distant location where, depending on the final usage, the liquid is either stored as liquid, transferred into another insulated liquid container, or converted to gas, warmed to near ambient temperature, and compressed to high pressure for storage in cylinders. In the case of compression, the process of warming the gas to ambient temperature and then compressing it to high pressure requires; a large capacity heat exchanger and a source of heat (approximately 6700 BTU/thousand standard cubic feet or 1508 Joules/gram), and a compressor containing usually 4 or 5 stages with inter and after stage cooling requiring a driver (approximately 25,500 BTU/thousand standard cubic feet or 5740 Joules/gram), a cooling source (approximately 25,500 BTU/million cubic feet or 5740 Joules/gram), and devices to remove entrained contaminants namely, oil in the form of vapors used to lubricate the compressor.
Capital cost of this equipment is large. Usually incomplete oil removal is not only objectionable but often hazardous since the helium may be used in the diving industry as a breathing gas carrier. Equipment of this size usually is noisy, generally not transportable and requires, inter alia, constant supervision while in operation, continual analysis of compressed helium and frequent maintenance.
U.S. Pat. No. 4,156,584 is one example of a helium pump used to compress and transfer liquefied gas but one that will not in and of itself be able to accomplish the foregoing objectives.